The present invention is directed to improved unplumbed sterilizers.
Unplumbed sterilizers are conventionally provided with a reservoir for holding a liquid such as water which is used to produce steam within the sterilization chamber. Typically, unplumbed sterilizers are relatively small units which are relatively simple in construction as compared to permanently fixed sterilizers which are hooked up to a steam supply line and drain. Typically, these unplumbed sterilizers rely upon a steam trap for releasing trapped air or steam from the chamber. A problem associated with such sterilizers is that they cannot be automatically charged with the correct amount of water for a subsequent sterilization cycle when the door is closed following the completion of a prior sterilization cycle. Another problem associated with this type of sterilizer is the trapping of air within the chamber after a sterilization cycle has been completed. Because of the hysteresis of the steam trap, the trap may not open or it may open for only a short period of time, thereby trapping air within the chamber. Because air is an insulator, the effectiveness of a steam sterilization cycle remains in question so long as air remains in the chamber.
The improved apparatus and method of operation of this invention overcome or minimize the aforementioned problems of previous unplumbed sterilizers.
The present invention comprises an improved construction and control mechanism for unplumbed sterilizers. The sterilizers of this invention include a sterilizing chamber with an associated liquid reservoir, as is typical of unplumbed sterilizers. The chamber has the usual access door and means for converting liquid to steam. Liquid is introduced from the reservoir to an inlet to the chamber through a first passageway, such as piping. A first control valve is associated with the first passageway and is operative selectively to open or close as needed to permit or prevent the flow of liquid through the chamber inlet. A second passageway, extends from an outlet from the chamber, and conducts steam from the chamber to a drain system, the atmosphere or back to the reservoir. A second control valve is associated with the second passageway and is operative selectively to open or close, thereby to permit or prevent the exhaust of air and/or steam through the outlet. An important aspect of this invention is the sequencing of the first and second control valves in coordination with the several steps of a sterilization cycle. Proper sequencing may be achieved in various ways, but as presently envisioned, electronic control means, including sensing and timing components, are provided for this purpose. The apparatus of this invention makes available methods of operation not previously practicable to realize with unplumbed sterilizers.
At the commencement of a sterilization cycle, a load is placed into the sterilizing chamber, the door of the chamber is closed, the heating element associated with the chamber is turned on. The first valve is turned on to permit liquid to enter the chamber. The liquid is converted to steam. The control means operates to hold the second valve open during the liquid introduction step. Significantly, the second valve is held open after the first valve is closed; that is, after the appropriate amount of liquid has been charged to the chamber. The second valve will be closed by operation of the control means in response to events signalled by sensors within the chamber or timing elements associated with the control means. In any event, the second valve is prevented from closing until it is certain that all of the air has been displaced from the chamber.
According to certain embodiments of the invention, the control means, which ideally includes a microprocessor in association with a temperature sensor, a timer, solenoids connected to drive the first and second valves, and other circuit components, effects a sequence of operation of both the first and second valves. The first and second valves are both opened at the commencement of a sterilization cycle. The first valve is closed after a prescribed time or in response to a level indicator. The second valve is closed after a second prescribed time interval or in response to an indication of temperature conditions in the chamber. Preferably, the second valve is closed a selected time interval following the sensing of a selected temperature within the chamber.